Research and Development Services Leading to the Control of Electrical Properties of Materials for High Temperature Radomes
Abstract
Pure aluminas and a commercial high purity product were hot-pressed in an Ar atmosphere. Densities in the range 3.85 to 3.97 g/cc were readily obtained at 1650 to 1750 C and 3000 to 3500 psi. Although the specimens were apparently rendered completely free of C by annealing in O at 1500 to 1700 C, their dissipation factors were much higher than for sintered disks made from the same powders. Compositions were formulated containing a titanate phase whose temperature variation of k' is negative. At a level of 14% SrTiO3, the k' of a titanate-alumina ceramic varied only 2.8% between 25 and 500 C at 10 to the 6th power c/s and 1.0% at 4 x 10 to the 9th power c/s as compared to 5.5 to 6.8% for high purity aluminas. The stable coexistence of Al2O3 and SrTiO3 on firing suggests a eutectic system which is located in the composition interval 65 to 70% SrTiO3, and near 1625 C.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1961
- Accession Number
- AD0268035
Entities
People
- H. H. Nakamura
- Leon M. Atlas
Organizations
- IIT Research Institute